1. Technical Field
The present invention relates generally to thermal imaging systems, and in particular to a high speed hardware implemented loader for loading video signal data to a look-up table for video signal data compression without having to first load the data into the system processor, thereby freeing the processor for other functions and speeding up processing of the subject video signal data.
2. Discussion
Scanning thermal imaging systems are used in a variety of applications, including surveillance systems and target detection/recognition systems. Such systems typically incorporate a telescopic lens assembly coupled to a scanner. The scanner scans energy from a scene through an imager lens assembly onto a detector array having a plurality of photoelectrically responsive detector elements perpendicular to the scan direction. Each of these detector elements provides an electric signal proportional to the flux of infrared light on the particular detector element. Electric signals generated from the detector elements are subsequently processed by system sensor electronics to create an image that is displayed on a system output device. To improve sensitivity, some of these systems incorporate detectors parallel to the scan direction. The output of these detectors are delayed in time from each other such that, ideally, the scanned image is output simultaneously on all of the parallel detectors. The delayed outputs are then summed (integrated). This process is referred to as time delay and integrate (TDI).
In the above-mentioned thermal imaging systems, the system electronics must typically compress an input video signal from 15 bits typically down to as few as 8 bits for further video signal processing or display. This data compression is conventionally done directly through the system processor. The processor loads video signal data directly into a static RAM memory on an address by address basis. Subsequent to the processor reading data accumulated by means such as a histogram chip, the video data is compressed by the processor through a video compression function loaded into a look-up table. The processor programs the look-up table with video compression mapping data.
In conventional thermal imaging systems, the above-mentioned data compression approach was inherently slow, as the video signal data was loaded directly by the processor into the look-up table on an address by address basis. The data compression function, when combined with other competing demands on the processor, subsequently caused inherent loop delays and thus slowed overall system processing.
Thus, what is needed is a data compression system for a thermal imaging unit that bypasses the system processor in large part, thereby freeing up the system processor for other functions and thus speeding up data compression and overall system speed.